Characterisation of Ti1-xSixNy nanocomposite films

Ti1-xSixNy films were synthesised by RF reactive sputtering from Ti and Si elemental targets, in an Ar/N-2 gas mixture. XRD results revealed the devel opment of a two-phase system, composed of a nanocrystalline f.c.c. TiN (pha se 1: B1 NaCl type) and a second one (phase 2), where Si atoms replaced som e of the Ti ones, inducing a structure that we may call a solid solution. A n amorphous phase, supposed to be of silicon nitride, within grain boundari es seems to be also present, especially for high Si contents. TEM experimen ts confirmed the f.c.c.-type structure for phase 2, which is the only phase that develops without ion bombardment. The higher lattice parameter of pha se 1 (similar to 0.429 nm compared to 0.424 nm for bulk TiN) may be explain ed by the residual stress effect on peak position. The Ti replacement by Si would explain the low value of the lattice parameter for phase 2 (similar to 0.418 nm). All samples showed good results for hardness (Hv greater than or equal to 30 GPa), and Ti0.85Si0.15N1.03 at a deposition temperature of 300 degreesC showed a value of approximately 47 Gpa, which is approximately double that of pure TiN. For higher deposition temperatures, an increase i n hardness is observed, as demonstrated by this same sample, which at 400 d egreesC reveals a value of approximately 54 GPa. Similar behaviour was obse rved in adhesion, where this same sample revealed a critical load for adhes ive failure of approximately 90 N. In terms of oxidation resistance, a sign ificant increase has also been observed in comparison with TiN. At 600 degr eesC, the oxidation resistance of Ti0.70Si0.30N1.10, is already 100 times h igher than that of TiN. For higher temperatures this behaviour tends to be even better when compared with other nitrides. (C) 2000 Elsevier Science S. A. Al rights reserved.